Matthew, if you can isolate your plants from your system water (or protect your tank/system water) from over-spray I can give you a recipe I use and have I've had great success with against those pesky buggers...if you're interested...

The next day spray with plain water or worm tea if you can make some. After a few (2-3) days spray again with the oil mix if you see more mites (wait til the eggs hatch if you can hold out). Then again with water and so on...Eggs will often hatch like George says so I keep this up for a week or more. It's kinda a hassle, but it gets rid of them for me every time so far.

Don't be tempted to make the oil mixture stronger than 5% (above 7-8% and you will in definitely burn your plants...

Yeah I hate those fuckers. Because of them 2 or 3 times a week I break out the magnifying glass neurotically spot checking and inspecting the undersides of leaves...I must look like a total lunatic...but those things have caused me a lot of headache as well, in the past. and they are quite prevalent here. I've learned to catch them early on, and fare much better that way.

matthew ferrell said:

These pest in another life cost me a LOT of money. In my new life they just cause my strawberries to suck at life.

If you use soap, try Octagon, if you can find it. It's a bar soap which you can shave off and dissolve in hot water. It's very effective against spider mites. Remember that they inhabit the underside of leaves - not an easy place to spray. It kills by smothering and by changing the PH - why changing the PH kills them I don't remember but I do know that it works. I haven't used it in aquaponics. I've had spider mites once in the five months my system has been running and I hit them with a hard spray of water two or three times and they were gone completely. Good luck.